Due to advantages such as a small volume, a light weight, and high efficiency, a switching mode power supply has been applied more widely. Existing switching power supplies are classified into a voltage-mode switching mode power supply and a current-mode switching mode power supply, where a basic operating principle of the voltage-mode switching mode power supply is pulse width modulation (PWM) processing and filtering processing is performed on a direct current (DC) voltage signal that is input, error amplification is performed on the DC voltage signal for which filtering processing has been performed and the DC voltage signal is sent to a comparator; the comparator compares the error-amplified signal with a current signal obtained by sampling (also referred to as sample selection) from an inductor of a low-pass filter, a PWM signal with a certain duty cycle is generated according to a level signal generated after the comparison, and the PWM signal is used to drive a switch element such as a thyristor, so as to obtain a stable output voltage signal.
In existing power supply applications, due to factors of product space, costs, and miniaturization of external components, a higher switching frequency of a switching mode power supply is required; however, in a present switching mode power supply in a current mode, a comparator in a control loop needs to collect a current from an inductor using a sampling circuit, and a present sampling circuit has a delay constraint and cannot operate accurately at a relatively high frequency.